Conventionally, a driving scheme referred to as “CC (Charge Coupling) driving” has been adopted for an active matrix-type liquid crystal display device. The CC driving is disclosed in Patent Literature 1, for example. Taking disclosure of Patent Literature 1 as an example, the CC driving will be described as below.
The structure of a device realizing the CC driving is shown in an equivalent circuit of FIG. 8, and operating waveforms of various kinds of signals in the CC driving are shown in a timing chart of FIG. 9.
As shown in the equivalent circuit of FIG. 8, a liquid crystal display device that performs the CC driving is provided, inside an image display section 110, with: a plurality of source lines (signal lines) 101; a plurality of gate lines (scan lines) 102 that intersect with these source lines 101; switching elements 103 provided in the vicinity of the intersections; pixel electrodes 104 connected to the switching elements 103; a plurality of CS (Capacity Storage) bus lines (common electrode lines) 105 each pairing up with each of the gate lines 102 and disposed in parallel to the gate lines 102; retention capacitors 106 each one end of which is connected to each of the pixel electrodes 104 and each other end of which is connected to each of the CS bus lines 105; and counter electrodes 109 opposed via liquid crystal 107.
The switching element 103 is formed with amorphous silicon (a-Si), polycrystal polysilicon (p-Si), single crystal silicon (c-Si), or the like, and a gate-drain capacity 108 is formed, considering the structure of the switching element 103. The capacity 108 causes the phenomenon in which a gate pulse from the gate line 102 shifts a potential of the pixel electrode 104 to a negative side.
Further, such a liquid crystal display device is provided, outside the image display section 110, with a source line drive circuit 111 that drives the source lines 101, a gate line drive circuit 112 that drives the gate lines 102, and a CS bus lien drive circuit 113 that drives the CS bus lines 105.
Operating waveforms of various kinds of signals in the liquid crystal display device are as shown in FIG. 9. That is, a waveform Wg of a certain gate line 102 goes Von only in a H period (horizontal scanning period) in which the gate line 102 is selected, and holds Voff in the other periods. A waveform Ws of the source line 101 becomes a waveform such that a polarity is reversed every H period and the polarity is opposite in an adjacent H period on the same gate line 102 (line inversion driving), although amplitude of the waveform Ws varies depending upon a video image to be displayed. Note that since the case of FIG. 9 assumes that a uniform video image signal is inputted, amplitude of the waveform Ws is constant in FIG. 9.
In a Von period of Wg, the waveform Wd of the pixel electrode 104 is of the same potential as the waveform Ws of the source line 101 since the switching element 103 is brought into conduction. At the moment in time when Wg goes Voff, the waveform Wd of the pixel electrode 104 slightly shifts to a negative side via the gate-drain capacitor 108.
A waveform Wc of the CS bus line 105 goes Ve+ in a H period in which the corresponding gate line 102 is selected and in the subsequent H period. In a further subsequent H period, the waveform Wc is switched to Ve− and then holds Ve− until the next field. This switching allows the waveform Wd of the pixel electrode 104 to shift to a negative side via the retention capacitor 106.
As a result, the waveform Wd of the pixel electrode 104 obtains amplitude greater than that of the waveform Ws of the source line 101. This makes it possible to make the amplitude of the waveform Ws of the source line 101 smaller. This realizes a simplified circuit configuration of the source line drive circuit 111 and reduction of power consumption.
Citation List
Patent Literature 1
Japanese Patent Application Publication, Tokukai, No. 2001-83943 A (Publication Date: Mar. 30, 2001)